The invention relates to a lithium battery, at least comprising:
a negative electrode, comprising negative electrode material and a negative current collector;
a positive electrode, comprising positive electrode material and a positive current collector; a separator, separating the negative electrode and the positive electrode; and
a non-aqueous electrolyte solution between the negative and the positive electrode, wherein at least the negative electrode material and the positive electrode material are provided with a pattern of holes which accommodate a polymeric material which sticks and presses the negative electrode, the positive electrode and the separator together.
Due to a growing market for lightweight, portable cordless consumer products, such as CD-players, mobile telephones, laptop computers and video cameras, there is an increased need for high-density batteries. Specifically, very thin and flexible batteries are required. In order to provide for an acceptable portability, the batteries contained in said consumer products should provide the necessary amount of energy at the smallest possible weight and volume. However, the thinner the battery gets, the more difficult the application of pressure, which is needed to maintain sufficient contact between the respective components of the battery, becomes.
A battery according to the preamble is known from the International patent application with publication number 00/04601.
Said battery has thin and flexible form and provides at the same time a very high energy density. Moreover, the contact between the electrodes and the separator is obtained and maintained in a very efficient way. The battery can be packed in a thin walled can, as the walls of said can are not needed to maintain sufficient pressure on the respective components of the battery.
At higher temperatures the liquid electrolyte made up of low molecular weight organic molecules, sometimes tends to sublime, giving rise to the expansion of the packaging material around the battery.
It is an object of the invention to provide a battery according to the preamble, in which the above problem is avoided.
This object is achieved in a battery as specified in the preamble, characterized in that the non-aqueous electrolyte solution comprises a solution of lithium salts, solvent molecules and a polymer, forming a gel-electrolyte.
As a result of its lower vapour pressure, such gel-electrolyte will show a considerably reduced sublimation at higher temperatures, compared to the electrolyte used in the prior art. Therefore, by providing a gel-electrolyte between the positive and the negative electrode, it is prevented that the packaging material around the battery components expands at higher temperatures.
In order to decrease the tendency of the liquid electrolytes to sublime preferably polymeric gelling agents are used.
Such polymeric gelling agents can be brought into the battery stack, anode and cathode materials and/or into the separator separately. Various types of polymeric materials which can advantageously be used are described below in the exemplary embodiment
In a preferred embodiment, the separator comprises the gel-electrolyte and more preferably consists of the gel-electrolyte.
In this latter embodiment, the gel-electrolyte has to have sufficient mechanical strength to act as a separator between the positive electrode and the negative electrode. The xe2x80x98usualxe2x80x99. separator can then be omitted and can be replaced by the gel-electrolyte which then acts as a separator.